In many chemical processes it is often desirable to detect the presence, quantity, and/or qualities of certain chemicals of interest. For example, in many closed chemical processes (either batch or continuous) the generation or infiltration of certain deleterious chemicals can damage or ruin the effectiveness of the process. By continually or periodically monitoring such processes the presence and/or amount of a deleterious chemical may be timely reported and damage to the system may be averted. As another example many systems include a residual or “background” concentration of an undesirable chemical that is acceptable. However, once the background level increases to a certain threshold limit, the higher concentration of the undesirable chemical becomes unacceptable and some action must be taken to avert danger to persons or damage to man-made materials and/or the environment. Accurate and sensitive monitoring techniques are tools that are used for these and similar types of applications.
One difficulty in monitoring certain chemical processes is that such monitoring may in itself have a negative effect on a system being monitored. For example, the presence of a monitoring device may interrupt system flow or adversely affect system output quality. Often, negative effects associated with certain monitoring equipment are due to the size of the monitoring equipment or the requirement of actively interjecting such monitoring equipment into a system from outside the system. Additionally, many chemical monitor devices or monitoring systems are limited in that only the presence of a particular chemical may be indicated as opposed to indicating quantity and/or quality information.
What are needed therefore are chemical sensors that are capable of passively monitoring a particular application in-situ so that the application is substantially unaffected by the presence of the sensor. What are also needed are chemical sensors and/or sensor systems that are capable of generating accurate and detailed quantification information based on differences in temperature gradients over time. What are further needed are in-situ chemical sensors that are capable of indicating a threshold event using an expendable and very small sensing apparatus.